1. Field of the Invention
The present invention relates to a method of managing a memory such as an electrically erasable programmable read only memory (EEPROM). Such a memory may be used, for example, in a smart card.
2. Brief Discussion of the Related Art
In such a memory, the stored elements are generally organized in a hierarchy (or tree structure), and it is known to manage said elements by means of an element allocation table and/or by means of pointers. The elements are then said to be physically chained relative to one another since each element corresponds to a physical address. This correspondence appears in the element allocation table, thereby making it possible in theory to find a looked-for element quickly. A drawback of using an element allocation table is that it occupies a fraction of the memory space that is no longer available for storing data. In addition, any change in the hierarchy of elements, such as move, a deletion, or a creation of an element, requires a corresponding modification to the element allocation table, and for a deletion also requires any elements that are descendants of the deleted element, themselves to be deleted. Such updating of the element allocation table slows down management of the elements and mobilizes computer means to which the memory is connected.
These drawbacks are particularly troublesome when the memory being managed is used in a smart card: the memory is of relatively small size and smart card readers have limited computer resources.
In addition, when the memory contains elements that are freely accessible and elements that are of access that is restricted solely to authorized people, a non-authorized person might attempt to access the restricted access elements by requesting the pointer to go to the address of a freely accessible element while disturbing the operation of the pointer (e.g. by subjecting it to a laser beam). There is then a risk of the disturbance bringing the pointer to a restricted access element without it being possible to verify correspondence between the requested address and the element reached.
It would therefore be advantageous to have a method of managing memory that does not have the above-mentioned drawbacks.